Conventionally, oxidation hair dyeing agents containing a p-phenylenediamine-type oxidation dye or an aminophenol-type oxidation dye, which are synthetic dyes, are widely used. Usually, the oxidation hair dyeing agent is a two-agent type hair coloring agent prepared by mixing a first agent and a second agent, wherein the first agent contains an oxidation dye and an alkaline agent, and the second agent contains a hydrogen peroxide solution as a main component. The Hydrogen peroxide solution has the functions of serving as an oxidizing agent for oxidatively polymerizing the oxidation dye to develop its color and a bleaching agent for decomposing the melanin pigment in the hair.
In use of such an oxidation hair dyeing agent, the first agent and the second agent are mixed immediately before application, and the mixture is applied onto the hair. When the oxidation hair dyeing agent is applied, the oxidation dye penetrated into the hair is oxidatively polymerized in the hair thereby to generate a bulky indo-dye, and the indo-dye develops its color. The indo-dye is not easily removed from the hair because of its bulkiness, making it possible to provide excellent color retention of the dyed hair and achieve a wide variety of color tones.
However, it is known that oxidation dyes may cause skin disorders. Furthermore, it has been pointed out that oxidation dyes are endocrine disruptors that adversely affect an ecosystem, and also that they allegedly produce cancers, allergies, and the like. For this reason, the use of oxidation hair dyeing agents is restricted in Europe and other countries.
Basic dyes are known as dyes that are safer than oxidation dyes. A basic dye is deposited as a result of its cation being ionically bonded to the anion of the keratin protein on the surface of the hair. Conventionally, the basic dye has been used, for example, as a hair manicure that lasts only about one to two weeks, as well as a color rinse and a color treatment that continue to provide color by being used several times a week.
For example, Patent Literature 1 below discloses, as a hair dyeing and hairdressing composition that achieves both a hairdressing effect and a hair dyeing effect, a hair dyeing and hairdressing composition containing a hair dyeing pigment that is at least one dye or pigment selected from an HC dye, a basic dye, a disperse dye and a natural pigment, as well as at least one α-hydroxy acid ester and/or at least one dialkyl carbonate, and at least one cross-linked polymer. Such a composition is a color treatment agent that fixes the dye by forming a polymer coating on the surface of the hair, and gradually colors the hair through frequent use. Accordingly, the composition disclosed in Patent Literature 1 is not used for cosmetic hair dyeing for dyeing black hair to a bright color, and cannot achieve long-term color retention by a single application.
Patent Literature 2 below, which discloses an invention made by the present inventors, discloses a hair dyeing method including a first step of applying, to hair, a base color dye liquid containing a basic dye and an HC dye serving as a main dye component and leaving the hair for a predetermined period of time, a second step of rinsing the hair on which the base color dye liquid has been applied, and a third step of, after the second step, applying an aqueous solution of tea catechin onto the hair and leaving the hair for a predetermined period of time. However, this technique is mainly used to fix the dye onto the hair that has been subjected to gray hair dyeing, and such a technique cannot be used for cosmetic hair dyeing for dyeing black hair to a bright color.